Defra officials say a diet low in animal proteins could make a difference in the fight against climate change. But they shy away from recommending a vegetarian lifestyle.

“These are not all-or-nothing choices and the government is not suggesting people should stop eating meat altogether,” said a Defra spokeswoman, who requested anonymity based on Defra policy.

Some campaigners see a missed opportunity. They say recommendations by governments to phase out meat-eating could have a far greater effect on reducing emissions than other global warming campaigns, like changing to low-energy light bulbs or taking public transportation.

“The answer is for people to move toward a plant-based diet if they’re serious about global warming,” said Justin Kerswell, a spokesman for Viva!, an animal rights group based in England. Such claims seem to be winning academic backing – and not only in green-minded Britain.